Ok, this is a scary thing for an even worse attack: the shooting happened right before screening. Everyone waiting to be screened panicked and ran, ALONG WITH THE TSA, through the screening area and into the “screened” terminal area!
Any terrorists now learn that you need one guy to do a suicide “distraction” like this, and then you can proceed into the terminal, guns (or worse) blazing.
I don't think that is any surprise. And once in there, they could be trapped in a dead end. I think all the exits are keyed.
It doesn't matter where the security point is located, the issue of congregation of people pops up there. The current location is about the best that can be done.